Understanding Abdominal Aortic Aneurysms

What is an abdominal aortic aneurysm (AAA)?

An aneurysm is a bulge in a blood vessel where the vessel wall has become weak or thin. As the wall weakens, that part of the vessel loses its ability to support the force of blood flow and begins to expand. Left untreated, the aneurysm may grow to several times the size of a normal vessel and could eventually rupture or burst. When an aneurysm occurs in the abdomen, it is called an abdominal aortic aneurysm, commonly abbreviated as AAA.

The aorta is the body’s main artery and it carries oxygen rich blood from the heart to the lower portion of the body. It runs from the chest to the abdomen, where it divides into two smaller arteries-the iliac arteries -that carry blood down into the legs. Aneurysms may occur in any blood vessel in the body but are most common in the aorta and the iliac arteries.

What causes AAAs?

It is not fully clear why aneurysms forms in the aorta. They can affect men or women of any age, although they are most common in men aged 65 and over and occur in about 1 in 25 men. Not all aneurysms are big enough to require treatment though;  only 1 in 100 AAAs are be large enough (>5cm in diameter) to require surgery.

As people grow older, some of the supporting tissue in the aortic wall can be lost and This explains why aneurysms are more common in older people. A person’s genetic make-up also plays a role as you have a much higher chance of developing an AAA if one of your immediate relatives (parent, brother, or sister) has, or has had a AAA. Other risk factors that increase the chance of getting an aneurysm include smoking, high blood pressure, emphysema and obesity.

Why are AAAs a concern?

The main concern is that the aneurysm might rupture. The wall of the aneurysm is weaker than a normal artery wall and may not be able to withstand the pressure of blood inside. If a rupture does occur, it may lead to severe internal bleeding, which can be fatal. It is important to remember though that most AAAs do not rupture.

What are the symptoms of an AAA?

In most cases there are no symptoms and when diagnosed with an AAA, 7 in 10 people will not have had any symptoms due to it. The expansion of the aneurysm does not cause any symptoms unless it becomes large enough to put pressure on nearby structures and this can lead to mild abdominal or back pain. As there are many other causes for these symptoms, it can be difficult to diagnose aneurysms at this stage, and a diagnosis might not be made until the aneurysm is large enough to be felt by a doctor when they examines your abdomen.